02 GEOLOGY OF THE LOTHIANS. 



rock are only to be explained by referring them to altering 

 agents of great power, agents of which the effects are visible 

 more or less in almost every stratified rock of any extent. 

 In intensely heated igneous matters rising through beds of 

 coal under a great compressing power, circumstances may 

 be found adequate to produce an alteration from the more 

 evident vegetable product to this highly crystalline mineral. 

 Many greenstones in the Lothians (Bathgate, Uphall) 

 contain coaly matter so disseminated through them, that it 

 is only by the bituminous odour which they give out when 

 struck that its presence can be recognised ; this case is si- 

 milar, and may be explained in the same way. The glance- 

 coal of the Calton Hill is interesting, as it is connected with 

 some views relative to the origin of veins. Veins of calcareous 

 spar are in many instances well explained by an infiltration 

 from above; here, however, such an origin is rendered 

 doubtful from the fact of such a mineral as glance-coal oc- 

 curring in them ; and we appear to have a more probable 

 explanation of some, as those of this locality, if we con- 

 sider them as being produced by changes altering enveloped 

 masses of limestone and coal. This explanation, however, 

 rests principally on the supposition that glance-coal is of a 

 vegetable nature. About a mile to the east of Edinburgh, 

 at Lochend, greenstone occurs overlying strata of sandstone, 

 and dipping to the east. Imbedded in this greenstone, there 

 are numerous fragments of slate-clay, all of which are com- 

 pletely changed in mineralogical character : veins of calca- 

 reous spar traverse the greenstone, in which occur minute 

 disseminated masses of sulphuret of lead. Near Restalrig, 

 a village about half a mile to the east of Lochend, two 

 beds of greenstone occur' in the sandstone strata, both of 

 these also dipping to the east. The greenstone of Restal- 

 rig is in general fine granular, and sometimes passes into 



